Contraceptive Activity Research Articles

“In the Name of Forests”: Highlights of the History of Family Planning in Costa Rica

The introduction of family planning in Costa Rica during the early 1960s is commonly thought to have been a health endeavour. This work shows that, instead, a concern with the environment, especially deforestation, was fundamental for starting the provision of contraceptives. The analysis traces the origins of contraceptive activities in Costa Rica to Turrialba, a little rural town which was, from the late 1940s, the experimental laboratory of the Interamerican Institute of Agricultural Sciences. There, foreign land workers concerned with the negative effects of population growth on the environment set the pillars of what would become one of the most effective programs of family planning in Latin America. This analysis situates Turrialba's local” endeavour in a broader context characterized by an increasing preoccupation with population growth in third world countries, and traces the specific ways in which these broader preoccupations made the contraceptive project in Turrialba, and later across Costa Rica, feasible.

Evaluation of reversible contraceptive activities of methanol extract of Annona squamosa(Linn.) stem bark in male rats

The present study was undertaken to evaluate the contraceptive activities of methanol stem bark extract of Annoa squamosa L. (Annonaceae) with their respective reversibility in male rats. Proven fertile male rats were gavaged 100% methanol extract of A. squamosa stem bark at the dose level of 50, 100 and 200 mg/rat/day for 60 days. Fertility was reduced by up to 100% at the dose level, 200 mg/rat/day. Sperm motility, density as well as other parameters related to the fertility were reduced significantly. The extract caused a marked reduction in the number of testicular cell population, seminiferous tubular diameters as well as the number of mature Leydig cells. The serum testosterone level was also decreased significantly. The findings of the study support claims of contraceptive properties of Annoa squamosa. This contraceptive activity was however, reversible after withdrawal of the drug treatment.

Formulation studies on the seeds of <i>Ricinus Communis Linn.</i> fam. Euphorbiaceae

Ricinus communis Linn. Family- Euphorbiaceae (castor oil plant) has been used widely as a contraceptive herbal drug in Nigeria, Africa and some countries in the Middle East. The efficacy of the seeds as a contraceptive drug has been confirmed by many scientists working independently in different locations around the world. With adequate information on the efficacy of these seeds, it became necessary to conduct a formulation study in order to develop a suitable and stable dosage form for this drug. The physical and chemical properties of the seeds used locally in Nigeria were determined and did not differ significantly from the properties of R. communis L. described in the African Pharmacopoeia. A total ash of 3.1% and alcohol soluble extractive value of 52.4% were obtained for the seeds while phyto-chemical screening revealed that the seed extract contained steroids and alkaloids. For safety and efficacy, the LD50 was determined and was found to be 13.17g/kg. The formulation studies revealed that 10 %starch mucilage was the best binder for the formulation of the granules while lactose at aconcentration of 75% was the best diluent for the drug. Characterization of the dosage forms produced showed that increases in compression pressure resulted in correspondent increase in the hardness, tensile strength, packing fractions and disintegration time. Administration of the dosage forms to albino rats, showed significant contraceptive activity (80%).

Structure of Insoluble Rat Sperm Glyceraldehyde-3-phosphate Dehydrogenase (GAPDH) via Heterotetramer Formation with Escherichia coli GAPDH Reveals Target for Contraceptive Design

Sperm glyceraldehyde-3-phosphate dehydrogenase has been shown to be a successful target for a non-hormonal contraceptive approach, but the agents tested to date have had unacceptable side effects. Obtaining the structure of the sperm-specific isoform to allow rational inhibitor design has therefore been a goal for a number of years but has proved intractable because of the insoluble nature of both native and recombinant protein. We have obtained soluble recombinant sperm glyceraldehyde-3-phosphate dehydrogenase as a heterotetramer with the Escherichia coli glyceraldehyde-3-phosphate dehydrogenase in a ratio of 1:3 and have solved the structure of the heterotetramer which we believe represents a novel strategy for structure determination of an insoluble protein. A structure was also obtained where glyceraldehyde 3-phosphate binds in the P(s) pocket in the active site of the sperm enzyme subunit in the presence of NAD. Modeling and comparison of the structures of human somatic and sperm-specific glyceraldehyde-3-phosphate dehydrogenase revealed few differences at the active site and hence rebut the long presumed structural specificity of 3-chlorolactaldehyde for the sperm isoform. The contraceptive activity of alpha-chlorohydrin and its apparent specificity for the sperm isoform in vivo are likely to be due to differences in metabolism to 3-chlorolactaldehyde in spermatozoa and somatic cells. However, further detailed analysis of the sperm glyceraldehyde-3-phosphate dehydrogenase structure revealed sites in the enzyme that do show significant difference compared with published somatic glyceraldehyde-3-phosphate dehydrogenase structures that could be exploited by structure-based drug design to identify leads for novel male contraceptives.

Nitric Oxide—Dependent Human Acrosomal Loss Induced by PPCM (SAMMA) and by Nitric Oxide Donors Occurs by Independent Pathways: Basis for Synthesis of an Improved Contraceptive Microbicide

PPCM (previously designated sulfuric acid-modified mandelic acid [SAMMA]) is a contraceptive microbicide in preclinical development. Its contraceptive activity is attributable in part to its ability to promote premature acrosomal loss. Prior studies showed that PPCM-induced human acrosomal loss (PAL) is Ca(2+)-dependent. This study was carried out to determine transduction elements downstream from Ca(2+) entry. PAL is inhibited by inhibitors selective for endothelial-type nitric oxide synthase. PAL is completely inhibited by 0.1 microM ODQ (soluble guanylate cyclase inhibitor). PAL is inhibited by protein kinase G inhibitors with selectivity for the type II isotype. Several inhibitors of the nitric oxide/cyclic guanosine monophosphate (cGMP)/protein kinase G pathway induce Ca(2+)-dependent acrosomal loss when added alone. These responses are inhibited by nifedipine, a blocker of Ca(v1.x) voltage-dependent channels. Acrosomal loss induced by the nitric oxide donor SNAP (SNAL) does not require added Ca(2+). Sperm production of nitric oxide is increased by PPCM, an effect inhibited by nitro-L-arginine (nitric oxide synthase inhibitor). Although inhibited by ODQ, SNAL and acrosomal loss induced by other nitric oxide donors are unaffected by KT5823 (protein kinase G inhibitor). Unlike PAL, SNAL is partially inhibited by KT5720 (protein kinase A inhibitor) and genistein (protein tyrosine kinase inhibitor). Acrosomal loss response to PPCM and SNAP added in combination suggests that these agents act by independent mechanisms. A PPCM derivative was synthesized, in which a nitric oxide donor was esterified to PPCM (NOSPPA-23). NOSPPA-23 induces acrosomal loss with or without added Ca(2+). The ED(50) of NOSPPA-23 (4.8 nM) in the presence of Ca(2+) is 35-fold less than that of PPCM. These findings suggest the following: 1) elements responsible for PAL include endothelial nitric oxide synthase, soluble guanylate cyclase, and type II protein kinase G; 2) the resting state of the nitric oxide/cGMP/protein kinase G pathway is a determinant of acrosomal status; 3) PPCM and nitric oxide donors induce acrosomal loss via nitric oxide, but through independent pathways; and 4) covalent attachment of a nitric oxide donor to PPCM provides synergistic efficacy as a stimulus of acrosomal loss. Further studies with this novel prototype as an improved contraceptive microbicide are warranted.

Dermaseptins and magainins: antimicrobial peptides from frogs' skin-new sources for a promising spermicides microbicides-a mini review.

Sexually transmitted infections (STIs) and human immunodeficiency virus (HIV), the causative agents of acquired immunodeficiency syndrome (AIDS), are two great concerns in the reproductive health of women. Thus, the challenge is to find products with a double activity, on the one hand having antimicrobial/antiviral properties with a role in the reduction of STI, and on the other hand having spermicidal action to be used as a contraceptive. In the absence of an effective microbicide along with the disadvantages of the most commonly used spermicidal contraceptive worldwide, nonoxynol-9, new emphasis has been focused on the development of more potential intravaginal microbicidal agents. Topical microbicides spermicides would ideally provide a female-controlled method of self-protection against HIV as well as preventing pregnancies. Nonoxynol-9, the only recommended microbicide spermicide, damages cervicovaginal epithelium because of its membrane-disruptive properties. Clearly, there is an urgent need to identify new compounds with dual potential microbicidal properties; antimicrobial peptides should be candidates for such investigations. Dermaseptins and magainins are two classes of cationic, amphipathic α-helical peptides that have been identified in the skin extracts of frogs Phyllomedusa sauvagei and Xenopus laevis. Regarding their contraceptive activities and their effect against various STI-causing pathogens, we believe that these two peptides are appropriate candidates in the evaluation of newer and safer microbicides spermicides in the future.

Analgesic effects of various extracts of the root of Abutilon indicum linn

Purpose : Abutilon indicum (Linn.) sweet (Malvaceae) commonly called 'Country Mallow' is a perennial plant up to 3 m in height. It is abundantly found as a weed in the sub-Himalayan tract and in the hotter parts of India. The plant is traditionally used for treatment of several diseases like bronchitis, body ache, toothache, jaundice, diabetes, fever, piles, leprosy, ulcers, cystitis, gonorrhea, diarrhea, and so on. Abutilon indicum Linn. is reported to have hepatoprotective, hypoglycemic, antimicrobial, male contraceptive, and antidiarrheal activities. The present study was done to evaluate the analgesic potential of various extracts of the root of Abutilon indicum Linn. Materials and Methods : The powdered root (900 g) was subjected to successive solvent extraction, with solvents in increasing order of polarity, namely, petroleum ether (60 - 80΀C), methanol, and ethanol, using the soxhlet apparatus for 72 hours. The marc was extracted by cold maceration for 72 hours, to obtain a water-soluble extract. The peripheral analgesic activity was studied using acetic acid-induced writhing method in Swiss albino mice (20 - 30 g), while the central analgesic activity was evaluated by the tail flick method and the tail immersion method. Results : Results indicated that all the tested extracts, except the methanol extract, exhibited significant analgesic activity in both animals' models. Petroleum ether extract showed higher analgesic activity. The activity may be related to the central mechanism or may be due to the peripheral analgesic mechanisms. Conclusion : The present study authenticates the traditional use.

Teen Pregnancy in Texas: 2005 to 2015

Texas birth records and population projections were used to simulate pregnancy rates among women ages 15-19 years from 2005 to 2015. Monte Carlo simulation based on historical rates of natural increase, contraceptive failure and sexual experience among racial/ethnic groups of teenaged women was used for numerical projections. These projections were used in a systems dynamics model which posits teen pregnancy risk as a stochastic process of contraceptive failure and sexual activity. The PRI was constructed as a logistic function of sexual experience, the weighted average contraceptive failure rates and time-varying probabilities of natural increase among racial/ethnic sub-groups of adolescent women. From 2005 to 2015, the number of adolescent, Hispanic females in Texas is expected to increase by 45%. During this same period, the expected pregnancy risk for 15 to 19 year old females is expected to increase to 13% or 127 per 1,000 women. This increase is due largely to the rise in the pregnancy risk among the growing population of Hispanic adolescents. Changing population characteristics in Texas and differences in sexual activity and contraceptive failure among racial/ethnic groups indicate that teenage pregnancy will not continue to decline in the coming decade. The adolescents most at risk for pregnancy are expected to increase significantly. Pregnancy prevention programs need to be intensified and adapted to the changing Texas social climate in order to preempt dramatic increases in teenage pregnancy.

Persistence of an Intact Endometrial Matrix and Vessels Structure in Women Exposed to VA-2914, a Selective Progesterone Receptor Modulator

VA-2914 is a selective progesterone receptor modulator with potential contraceptive activity that induces amenorrhea, whereas progestins cause endometrial spotting and bleeding. This abnormal bleeding due to progestins is a consequence of focal stromal proteolysis by an increase in naked vessel size and density. Our objective was to quantify the effects of VA-2914 on endometrial vascularization, fibrillar matrix, and vascular endothelial growth factor (VEGF)-A expression in endometrial biopsies from 41 women before and after 12 wk daily treatment with a placebo, or 2.5, 5, or 10 mg VA-2914. Collagen fibrillar network was stained by silver impregnation. Vessel area, density, and structure were quantified with a computer-assisted image analysis system after double immunostaining using an anti-von Willebrand factor (endothelial cells) and an anti-alpha smooth muscle actin (vascular smooth muscle cells) marker antibody. VEGF-A mRNAs were quantified by RT-PCR and localized by immunohistochemistry. The endometrial vessels, collagen network, and mRNA levels of VEGF-A were identical during the luteal phase at baseline and in VA-2914 treated women. VEGF-A distribution was unchanged. VA-2914 does not alter the endometrial matrix and cells, and does not modify the endometrial vessel morphology as compared with baseline biopsies.

Pharmacophore search for anti-fertility and estrogenic potencies of estrogen analogs

Estrogen mediates its action following binding to the estrogen receptor to form an estrogen-receptor complex. The complex initiates gene transcription and produces estrogen-induced cell and/or tissue responses, i.e., estrogenic actions. High doses of estrogen can be used effectively as a contraceptive but are associated with side effects. Considering the long-term benefit-to-risk ratio of estrogen analogs as oral contraceptives, the present study was performed to deduce the active pharmacophore features required to differentiate the anti-fertility potency from the estrogenic activity of the steroidal motif. Implementing classical quantitative structure-activity relationship (QSAR) studies, substitution by an electron-donating group at the C17 position and the presence of a hydrogen bond acceptor at C11, along with the orientation and conformational rigidity of the molecule, were found to be critically important features for estrogenic potency, including anti-fertility activity. However, low electron density at C2 and high electronegativity at C16, which may be due to substitution on those and/or neighboring atoms, favor contraceptive potency, whereas high electron density at C5 and substitution by an electron-withdrawing group at C7, which may confer hydrophobicity on the steroidal scaffold and an overall increment of electron affinity of the molecule, are favorable for estrogenicity. Further CATALYST-based 3D space modeling demonstrates that the presence of the aromatic ring (ring A), hydrophobic zone (ring B), and hydrogen bond acceptor at C17 in ring D, along with steric influence due to conformational rigidity of the compound, impart estrogenic contraceptive activity, but the presence of a second acceptor in ring A, and the critical distances between these features, selectively differentiate the anti-fertility potency from the estrogenic activity.

Synthesis and in vivo evaluation of 11-substituted estradiol derivatives as anti-implantation agents

Synthesis of 11-substituted estradiol derivatives ( 12– 17) has been carried out by the Grignard reaction with alkyl, allyl, and benzyl halides on 17β-hydroxy-3-methoxy-11-oxo-estra-1,3,5(10),8(9)-tetraene ( 10). The novel compounds ( 10 and 12– 17) were evaluated for their preliminary post-coital contraceptive (anti-implantation) activity in Sprague–Dawley rats. The tested compounds were administered orally and showed significant anti-implantation activity. Compound 13 is the most potent compound in the series which showed 100% contraceptive efficacy at 1.25 mg kg −1.

Contraceptive applications of progesterone receptor modulators

Currently developed progesterone receptor modulators (PRMs) are steroid-derived compounds with mild or potent antiprogestin activity. PRMs may exert a contraceptive activity by different mechanisms such as blockade of ovulation and endometrial desynchronization. Their potential clinical applications are manifold and are very promising in major public health areas, including emergency contraception, long term oestrogen-free contraception (administered alone, or in association with a progestin-only pill to improve bleeding patterns), endometriosis and myoma treatment. The mechanisms of their anti-ovulatory effects and of the endometrial modifications elicited during long term PRM treatment are still not fully elucidated. In future clinical applications, PRMs will be administered orally, via intrauterine systems or vaginal rings.

Evaluation of developmental toxicity of microbicide Nisin in rats

In the present study, we have investigated the developmental toxicity of a naturally occurring peptide, Nisin in rats in order to determine its suitability as a safe vaginal microbicide. Our earlier studies indicated that, Nisin is a dual function microbicide having contraceptive and antibacterial activities. However, as part of the safety evaluation of any vaginal microbicide, it is essential to determine its teratogenic potential in a suitable animal model before it is found suitable to enter clinical trials. Sixty pregnant rats allocated into four groups were orally administered with 10, 25 and 50 mg Nisin/kg/day from day 6 to day 15 of gestation. Individual food/water consumption and body weight changes were measured daily. Nisin did not cause maternal mortality nor did the treated animals show any clinical signs of toxicity when compared to the control animals. There were no biologically significant differences in maternal liver, kidney, thymus, ovary, gravid and empty uterine weights. Mean number of corpora lutea and implantation sites also did not differ in the treated groups when compared to their respective controls. All the fetuses were weighed, sexed and examined carefully for externally visible malformations. No gross external fetal alterations were observed at any dose tested. When stained by the double staining method, no skeletal malformations and visceral defects were observed in the fetuses. The growth and reproductive performance of the F1 progeny was also unaffected. In conclusion, Nisin shows unique clinical potential as a safe prophylactic microbicide to curb the transmission of STIs/HIV and unintended pregnancies.

The Contraceptive Effect of the Extract Methanol of The Leaves Hydrocotyle Javanica Thumb on Female Mice

The aim of this study is to investigate the contraceptive effect of the extract methanol of the leavesHydrocotyle javanica Thumb and its effect threat of implantation, the quantity and condition of fetuses,histology appearance of the ovary and uterus and rate of pregnancy. The female mice were given orallyeither methanol extract of leaves, for 10 days in various doses: 20, 40, 60, and 80 gram/kg BW. On day20, the mice were mated and when pregnancy occurred, treatment was stopped. On day 17 of pregnancy,the mice were sacrificed: uterus and ovaries were examined histologically. In conclusion, methanol extractof Hydrocotyle javanica Thumb shows contraceptive activity (P 0.05).Keywords: extract methanol, Hydrocotyle javanica Thumb, contraceptive

Evaluation of contraceptive activity of methanol extract of Dendrophthoe falcata stem in male albino rats

The present study was undertaken to evaluate the contraceptive efficacy of methanol extract of Dendrophthoe falcata Ettingsh (family-Loranthaceae), stem in male albino rats as reported in folk remedies. Adult proven fertile male rats were gavaged methanol extract of D. falcata stem at 50, 100 and 200 mg/rat/day for 60 days. The activity was compared with standard drug, i.e. Lonidamine. On day 61 the animals were autopsied and the testes, epididymides, seminal vesicle and ventral prostate were dissected out and weighed. Sperm motility and density and serum testosterone level were assessed. The sperm motility and density were significantly reduced. The histoarchitecture of testes revealed degenerative changes in the seminiferous tubules, arrest of spermatogenesis at the stage of round spermatid. Serum testosterone levels were decreased significantly in all treatment groups. It is concluded that D. falcata methanol stem extract showed a significant effect on fertility in male rats as reported in folk remedies.

Reversible contraceptive efficacy of methanol extract of aerial parts of Gynandropsis pentaphylla in male albino rats

In spite of the considerable development in contraceptive technology, search for male antifertility agents in plants continues to be a potential area of investigation. Many plants have been known to possess antifertility activity but limited attempts have been made to scientifically evaluate these claims. Hence the purpose of this study was to evaluate the antifertility and reproductive toxicity potential of Gynandropsis pentaphylla DC. (Capparidaceae) in male wistar rats. Oral administration of 100% methanol extract of aerial parts of G. pentaphylla (Capparidaceae) at the dose level of 20mg/rat/day male albino rats for 60 days did not decrease body weight, while the testes and epididymides were significantly reduced, seminal vesicles and ventral prostate showed a significant reduction (P≤0.001). Treated animals showed a notable depression of spermatogenesis. As a result of 20mg/rat/day extract feeding, the preleptotene spermatocytes, secondary spermatocytes, round spermatids and the mature Leydig cells decreased. At this dose level Leydig cell nuclear area and cytoplasmic area, as well as the cross sectional surface area of Sertoli cells, were significantly reduced (P≤0.001) when compared to controls. The reduced sperm count and motility resulted in 100% negative fertility. A significant fall in the total protein and sialic acid content in the testes, epididymides, seminal vesicle and ventral prostate, as well as in the glycogen content of testes was also observed. However a most exciting observation is that all the parameters were found in a non-significant manner after withdrawal of the drug. In conclusion methanol extract of G. pentaphylla have contraceptive activity in male rats with their reversible nature.

SAMMA Induces Premature Human Acrosomal Loss by Ca2+Signaling Dysregulation

SAMMA is licensed for development as a contraceptive microbicide. Understanding mechanisms of its biological activity is prerequisite to designing more active second generation products. This study examined Ca(2+) involvement in SAMMA-induced premature acrosomal loss (SAL) in noncapacitated human spermatozoa. SAMMA causes acrosomal loss (AL) in a dose-dependent manner (ED(50) = 0.25 microg/mL). SAL requires extracellular Ca(2+) (ED(50) = 85 microM). SAL is inhibited by verapamil (nonspecific voltage-dependent Ca(2+) channel blocker; IC(50) = 0.4 microM), diphenylhydantoin and NiCl(2) (T-type [Ca(v)3.x] channel blockers; IC(50) 210 microM and 75 microM, respectively). Verapamil blockade of L-type (Ca(v)1.x) channels is use-dependent; activated channels are more sensitive to inhibition. However, verapamil inhibition of SAL does not increase after repeated SAMMA stimulation. SAL is unaffected by 10 microM nifedipine (selective L-type channel blocker). This contrasts to 40% inhibition (P < .001) of AL induced by 1 microM thapsigargin (Ca(2+)-ATPase inhibitor; releases intracellular Ca(2+) stores, promotes capacitative Ca(2+) entry). SAL is unaffected by 1 microM BAPTA-AM (intracellular Ca(2+) chelator), and 50 microM 2-APB (blocks InsP3 receptors and store-operated channels). This contrasts with thapsigargin-induced AL, inhibited nearly 65% by BAPTA-AM (P < .005) and 91% by 2-APB (P, .001). The results suggest that SAL is mediated by Ca(2+) entry through channels pharmacologically similar to the T-type (Ca(v)3.2) class. This process appears distinct from that caused by physiological stimuli such as progesterone or zona pellucida-derived proteins. SAMMA's contraceptive activity may be caused by induction of premature AL through dysregulation of Ca(2+) signaling.

Avaliação do extrato hidroalcoólico de Mentha crispa sobre a performance reprodutiva em ratos Wistar

Mentha crispa (Lamiaceae) is commonly known as hortela-da-folha-miuda. The hydroalcoholic extract (HAE) from the leaves and stem of Mentha crispa possesses amebicidal (Entamoeba histolytica) and giardicidal (Giardia lamblia) activity and it is commercially used in the production of the phytoterapic Giamebil plus®. The effects of the subchronic administration of the HAE of Mentha crispa were investigated on reproductive performance in adult Wistar rats. Three groups of male rats (n=6-12/group) were orally treated daily for 30 consecutive days with the HAE at doses of 0.5 and 1.0 g/kg or distilled water (control group). Then, the reproductive indices, the organ weight and the morphologic analysis of testicle, epididymis and vas deferens were determined. There were no signs of toxicity or deaths during the period of treatment. Furthermore, the reproductive indices, the organ weight and the macroscopic and microscopic morphologic analysis of the organs were not altered by subchronic administration of the HAE of Mentha crispa. It shows that the subchronic administration of the HAE of Mentha crispa (Giamebil plus®) did not possess contraceptive activity on the reproductive system of Wistar rats.

Dose-related actions of GnRH II analog in the cycling rhesus monkey

Introduction Gonadotropin-releasing hormone (GnRH) II expression, specific high-affinity receptors for GnRH II and its potent bioactivity in human and baboon tissues led us to hypothesize that GnRH II is a bioactive peptide in primates. We recently demonstrated the contraceptive activity of GnRH II analog in rhesus monkeys. In the present experiment, we extended those studies to the dose-related action of this analog on parameters of luteal function and conception. Methods GnRH II analog (0–32 μg/day) or saline was administered via osmotic minipumps for 6 days (Days 1–6 postovulation) to regularly cycling rhesus monkeys mated with fertile males around the time of ovulation. Cycle dynamics was monitored through circulating luteinizing hormone, progesterone and estradiol. Pregnancy was determined by circulating chorionic gonadotropin concentrations. Results Progesterone production (Days 3–11) was significantly less (p<.05) for animals treated with 2, 4 or 8 μg/mL GnRH II analog than for controls, yet with higher doses of GnRH II analog (i.e., 16 or 32 μg/day), luteal progesterone was not different from that of saline-treated controls. The length of the luteal phase in all treated groups was similar to that of controls. In 18 animals mated at the time of ovulation and then treated with GnRH II analog (2–32 μg/day), no pregnancies resulted. In saline-treated controls, five of eight animals (62.5%) became pregnant. Thus, the contraceptive activity of this GnRH II analog did not correlate with luteal progesterone inhibition. Conclusions These data demonstrate a dose-related action of GnRH II analog on luteal progesterone and establish the contraceptive activity of 2–32 μg/day GnRH II analog administered postovulation.

Avian Contraceptive Tools: One Size Does Not Fit All

Author(s): Yoder, Christi A.; Miller, Lowell A. | Abstract: Avian contraception is a nonlethal management tool that can be utilized in conjunction with other management techniques to help manage bird populations causing damage. Because management situations vary with respect to the type of damage, species involved, location, and nontarget hazards, it is necessary to develop multiple contraceptive tools to allow management flexibility. DiazaCon™ and nicarbazin have already been developed at the National Wildlife Research Center as avian contraceptives. Although both of these are promising contraceptive agents, more are needed for a wider variety of situations. Current research is focusing on other cholesterol inhibitors, inhibitors of the P450 side chain cleavage enzyme, and aromatase inhibitors. Because cholesterol is needed for steroid reproductive hormone production, inhibition of cholesterol impairs reproduction by preventing the formation of the necessary hormones. The P450 side chain cleavage enzyme is needed to convert cholesterol to pregnenolone, the precursor to progesterone and testosterone. Progesterone is needed for egg formation, ovulation, and oviposition, and testosterone is needed for sperm production. Aromatase is needed to convert testosterone to estradiol, which is needed in females to stimulate the production of egg yolk precursors in the liver. Inhibition of either of these enzymes should result in impaired reproduction. In the future, natural plant products with contraceptive activity, such as neem seed, will also be investigated. Because development of avian contraceptives is time intensive, an efficient screening process needs to be in place. Population models can assist in choosing specific agents to test for a given species and management situation. Although contraception is unlikely to be useful as a stand-alone tool, it can be included in integrated management plans.